Generally, the Internet Protocol (IP) protocol and IP networks have been designed to support a single, best-effort class of service. IP networks have successfully transported TCP-mediated data traffic. As a result, there is a convergence effort to migrate all networked applications, such as voice and videoconferencing applications, to use IP networks as the common transport medium. Best-effort service, however, is not sufficient to meet the Quality-of-Service (QoS) needs of these next-generation applications, especially in an enterprise environment.
A challenging problem for IP networks is efficient admission control (AC). Admission control is required, for example, to support QoS for many inelastic applications. A number of techniques have been proposed or suggested for admission control in packet-switched networks. For example, resource-based admission control (RBAC) methods reserve sufficient network resources for an application on a per-flow basis to handle specified peak bandwidth needs. While generally providing guaranteed QoS, RBAC techniques ignore statistical multiplexing and are therefore inefficient in the sense that additional flows could typically be admitted without experiencing QoS degradation.
More recently, measurement-based admission control (MBAC) methods have been proposed that learn the statistics of network traffic by making on-line measurements. In addition to improving the number of calls supported within a given bandwidth, when compared to RBAC methods, MBAC methods require simpler traffic specifications and are simpler to analyze and design. MBAC methods may be categorized as passive, active, or hybrid techniques. Passive MBAC techniques measure statistics of actual bearer (non-synthetic) traffic. Active MBAC techniques probe the network with synthetic traffic. Hybrid methods combine passive and active methods to improve accuracy and reduce active traffic loads.
While existing MBAC techniques exhibit improved efficiency, by admitting a greater number of calls before unnecessary blocking is experienced, they suffer from a number of limitations, which if overcome, could further improve the utility and efficiency of admission control techniques in packet networks, such as IP networks. For example, such MBAC techniques are static, in the sense that, once configured, the admission control algorithm accepts or rejects a call based on current network conditions relative to fixed criteria. A need therefore exists for adaptive methods and apparatus for admission control. A further need exists for methods and apparatus for admission control that adjust one or more system parameters based on a performance metric.